Process of adhering textile fibers to rubbers and product thereof



United States Patent PROCESS OFADHERING TEX'HLEQFIBERS T -RUBBERS.ANDPRODUCT .THEREOF zEdward'.F.*Kalafus,;Akron, Ohio, assignor to .TheGeneral TirsfimdRubbtsr Company, Akron; Ohio, a corporation of i0 "NoDrawing. ApplicationFebruary' 9, "1953, Serial-N0. 335,997

8 Claims. ;(Cl. 154-439) This invention relates to adhesives andparticularly 'tolatex adhesives for'bon'ding fibers or cordsof cotton,rayon, nylon and the like to natural and synthetic rubbers.

"In themanufacture .of many "fabric-reinforced, molded .rubber articles,especially automobile tires, it .is desir'able to obtain strongadherence between the fabric and the rubber, and also high resistance todeterioration of the bond .with flexing of the structure. .'In the caseof pneumatic tires, thefflex-life of the carcass is probably the most.critical factor affecting thedifeoftiresin service. Long flex-life isdependent not .only upon the inherent flexibility of the carcassstructure and'the strength of the bond betweenthe tire fabric and the.adjacent-rubher, but also upon fatigue resistance underrepeated flexingover long periods o'ftime.

"Many adhesives known 'to produce .very strong :bonds between rubberandfabricare .entirely'unsuitable for many rubber "fabric structures'because ;the .bonds deteriorate or.the fabric ruptures .Whenthestructures are subjected to .repeated .flexing. "Thus flex life cannot'be .foretold from measurements ofbond strengths alone.

When cotton 'fabricsarecngployed in the production of fabric reinforcedrubber articles, it is possible "to calender the rubber into the fabricin such manner as to work the rubber between the fibers of theindividual cords or threads, thus obtaining a mechanical interlocking ofthe two materials, and this practice has been followed for many years.However, the mechanical "b'ond obtainable in this manner with cottonfibers is not en'tirely satisfactory, and the calendering process issubstantially inoperative when applied to most continuous syntheticfibers, such as rayon and nylon, which are formed into cords by atwisting process that leaves the cords practically devoid of intersticesinto which the rubberican be forced by the calendering rolls.

This problem of obtaining satisfactory adhesion between rubber and cordsof synthetic fibers wasrthe principal obstacle that delayed the use ofsuch fibersfin fabrics for pneumatic tire carcasses. The problem wasfinally solved to a degree, in the case of rayon, by theme "of mixturesof natural latex -andresorcinol or casein. "The casein-latex adhesivewas .comparatively' -fiexible"but'the strength and character of theadh'esivabond =obtained *le'ft much to be desired. The resorcinolformaldehyde latex mixture was developed and'widely useil'inthe tireindustry, particularly with "rayon fabrics. While "fair adhesion 'wasobtainable withthis adhesive, it *formed a relatively hard andstilf filmon 'theIfabri-cthat .ser'iously impaired its flexibility and 'flex lifeand the adhesionLbe- .tweensynthetic .rubber and fabrics was nowherenearly good as desired.

In accordance with the subjectinvention, Lhave ..dis covered an adhesivedip 'that strongly :adheres .to .the fabric andrubbertand which .at the.sametimeis relatively flexible. I

Alt is accordingly one object :ofth'e present invention 2,748,049Patented May 29, 1956 '2 'toprovidean inexpensive, relatively flexiblefiber-to-rubberradhesive.

"Itsis another'object of this inventionto provide a fiberto=ri1bberadhesiveinwhieh a firmbondbetweenthe fiber or fabric -and "rubber is"achieved. Other objects and advantages of'the subject invention ,willbecome apparent from the-following description thereof. 7

In accordance with this invention, I.have..discovered an adhesive dipcomprising "an aqueous .dispersion of ('d) 70'to"95'partsdry solidsweight'of a 'copolymer of "from 65 to '90'partsof 'aconjugated'diolefinic compound of less thanseven aliphatic carbon atoms and "fromv10 to '35 parts of an unsaturated "aldehyde of'the general "formulawhere "R is a bivalent aliphatic hydrocarbonradical of less than fourcarbon atoms (preferably methylene) and *R' is-a member of'agroupconsisting of hydrogen, methyl and ethyl and (I 5 to 30=partsbydry solids weight of a condensation product selected from the groupconsisting of phenol-formaldehyde, urea formaldehyde,casein-formaldehyde, "and "melamine formaldehyde. This dip forms aninexpensive, flexible,:and firm bond between fiber or fabric and rubber.

The conjugated 'diolefinic compound includes substirated andunsubstituteddiolfines of *less than seven aliphatic carbon atoms su'ch'asbutadienefdirnethyl butadi- 'ene, 'chl'oroprene, "isopren'e,-an'dcyanoprene.

"Suit-able alpha beta-unsaturate'd-aldehydes include acro- "lein,'rnethacrolin, alpha e'thyl *acrdlein, alpha methyl beta ethyl acrolein,'crotonaldehyde, an'dthe like. These 'a-ldehydes are included within thea general formula R.=corr0 in which R is a bivalent 'hydrocarbon of'less than four carbon atoms anduRis a member of the group consisting ofhydrogen methyl and ethyl. Methacrolein is the preferable .aldehydebecause it is commercially availablemndrreadilyi'fonns copolyrners:withthe diolefine.

The condensation product :lS :preferably primarily a-resorcinol-.formal"dehyfde condensation .product although any of thegroup-consisting of other phenol-formaldehyde, urea formaldehyde, casein'formaldehy'de, and mel amine-formaldehyde may alsobe used.Thecondensation product .is thus the product of a condensation reactionbetween an aldehyde.reac'tive compound (phenols,'urea, casein, andmelamine.) andan aldehyde, pref- :erablyiformaldehyde. .Resorcinolreso'les and resorcinol- .phenol' resoles;whetherzformed in situ'withintthe acrolein "or substituted :acrolein-diolefinic compound latexor formed .separately in aqueoussolution, are considerably superior -.toother condensation products in the adhesive -rnixture.

-.-In.raccordance-with thiszinvention, the copolymer .of the:conjugzited diolefinic compound and :unsaturated *al- -dehyde is,prepared. in-a. conventionalemulsion polymerizat-i.onirecipe and.reacted to almost percent con- -vension. .The diolefineshouldconstitutefrom :60 to 90 parts and preferablyraround 755 parts by weight:oftthe copolym'er :and ,tthe unsaturated aldehyde from to 35 ,parts bywveight and ;:preferably around '25 partszof the .copolymer.

Theresorcinol -.or other corresponding taldehyde reacillVE component 20fthe condensation:productrmay :be dissolved in water to which around 37per cent formaldehydethas been-added=together-withaxstrong baset-such as:sodium hydroxide. .The strong :base should generally constitutearound7.5 ,perx-cent or less of the resorcinol or -othencongponent.Theraqueoussolution-of the resole or condensation product or resin ismixed with the diolefine-aldehyde latex. The resole or other mentionedcondensation product or materials that form said condensation productshould constitute from to 40 parts and preferably around to 25 parts bysolids of the latex mixture. The condensation product forming the resoleor resole type resin forming materials should preferably be partiallyreacted or reacted so as to be only partially soluble in water.Sufficient water is then preferably added to give around per cent byweight overall solids in the final dip.

I have found it is preferable to first prepare the copolymer of thediolefine and unsaturated aldehyde and then add the partially condensedcondensation product. However, the ingredients, for example, theresorcinol or phenol may beadded to the latex in uncondensed form andthe entire' condensation may there take place in situ. The latex tendsto keep longer and be more stable if it is kept alkaline.

In accordance with this invention, the cord or fabric to be treated isdipped for one to two or three minutes in this latex dip and dried atfrom 75 to 140 C. for one to five up to twenty minutes'and thereaftercalendered into the rubber and cured therewith. Preferable dryingtemperature is around 100 C. and preferable drying time is around fiveminutes.

The following example illustrates this invention.

EXAMPLE 1 A series of butadiene-methacrolein latices were made up using180 parts of water, 75 parts of butadiene, parts of methacrolein, 5parts of soap, 2 parts of potassium persulfate, (a free radicalproducing catalyst) and .4 part of mixed tertiary mercaptans having anaverage of 16 carbon atoms as modifier. The reaction was carried out tosubstantially complete conversion. The resultant latex was mixed with aresole formed in situ by adding to the latex the amount of resorcinoland formaldehyde shown in table 1. The adhesion of the dip to both rayonand nylon'was tested and the results shown in table 1 were obtained.

ployed, and the force in pounds required to pull the cord free from theenclosing rectangles at either end was taken as the measure of thestrength of the adhesive bond obtained. Between the time when the cordswere clipped and dried and the time when they were tested, they werestored in closed glass containers to avoid the effects of non-uniformexposure.

Since the flex-life as well as the bond strength is important, theflex-life of fibers dipped in a dip of the subject invention was tested.This was done by using dip #2 of Example 1 in the construction ofseveral passenger car pneumatic tires. These tires were built in thecustomary manner. Similar tires employing a conventional butadiene-vinylpyridine copolymer compounded with resorcinol and formaldehyde as thedip were also secured. Both kinds of tires were driven loaded andunderinflated until they failed from flexing fatigue. The tires usingthe adhesive dip of the subject invention ran from 10 to 30 per centlonger than those using the conventional vinyl pyridine type dip.

In the above example, the amount of methacrolein may be varied and themethacrolein in the copolymer may be substituted in whole or in part byacrolein and other butadiene copolymerizable aldehyde as above pointedout to obtain some benefits of the emulsion although 'methacrolein isthe preferred comonomer. A styrene may be substituted for part of thebutadiene as above set forth. Part of all of the butadiene may besubstituted by other diolefinic compounds of less than 7 aliphaticcarbon atoms without much change in adhesive properties.

v In place of partoriall the resorcinol-formaldehyde resole in the aboveexample, I may use one or more of the other above noted aldehydecondensation products such as the condensation products of phenol andaldehyde, urea-aldehyde, melamine-aldehyde. When the novolac type ofphenol-aldehyde condensation products are used, care should be used toinsure stabilization of acid residue before introduction into a nonacidstable latex as is obvious to those skilled in the art. I can also addwith good results up to 10 to 15 parts of styrene or any styrene Table 1Percent Mole Ratio to I Parts Parts Parts Parts NaOH MethacroleinAdheslm Dip by wt by wt b wt b Wt Based No. Poly- Riasop- Ron R R N Imer o no esoresorayon y on,

cinol cinol Q lbs. lbs.

100 39. 3 10. 7 1. 18 2. 5 1 1 20. 3 12. 1 100 39. 3 l0. 7 2. 3G 5 1 116. 7 13- 4 100 39. 3 I0. 7 3. 4 7. 5 l l 22. 6 17. 0 100 39. 3 10. 7 3.93 10. 0 1 l 18. 1 14. 3 100 19. 64 5. 3G 0. 49 2. 5 (l. 5 U. 5 20. 718. 5 100 19. 64 5. 33 U. 98 5 U. 5 0. 5 21. 1 15. 7 100 19. 64 5. 36 l.47 7. 5 0. 5 U. 5 21. 7 .18. 9 100 19. 64 5. 36 1. 96 10 0. 5 U. 5 17. 514. 9 100 9. 72 2. 68 0. 24: 2. 5 O. 25 0. 25 15. 6 22. 8 100 9. 72 2.68 0. 48 5. 0 U. 25 0. 25 16. 5 19. 7 100 9. 72 2. 68 O. 72 7. 5 0. 25O. 25 18. 6 23. 4 100 9. 72 2. (i8 0. 97 10. 0 0. 25 O. 25 15. 2 18. 8

The adhesion tests by which the scope and utility of the invention havebeen determined, as described above, were all performed in the samemanner. Each adhesive dipped cord that was tested was anchored at eachend between pairs of rectangular pieces of uncured, highly-carbon-black-l0aded rubber compound. The rectangular pieces of rubber wereall of a uniform size, measuring 0.375xl.000x0.1100 inches. Each wasbacked on one side with cotton duck that was cemented thereto. Each endof the cord was placed between the rubber faces of that iscopolymerizable with butadiene to the monomer mixture from which thecopolymer is formed.

The aldehyde groups in the copolymer which result from the acrolein ormethacrolein and the'like are reactive .to resorcinol and otheraldehyde-reactive compounds used in preparing the condensation productin that some benefits are obtained without addition of formaldehyde orfree aldehyde to the latex along with the resorcinol. Much better,results are obtained, however, with the addition of a free aldehyde,particularly formaldehyde. Thecombination of free and polymer combinedaldehyde provides superior adhesion. When the latex must be stored forextensive periods, there is a tendency to gel 'unless the ratio ofresorcinol to total aldehyde is controlled.' Higher ratios of resorcinolor other phenol or urea to aldehyde tend to gel faster.

mole ratio of 1:1 or less for the aldehyde reactive compound forming thecondensation product,"such as resorcinol, to the free aldehyde, such; asformaldeyhde, is preferable in order to insure satisfactory storage. Theadhesion and gel time tend to decrease as the amount of resorcinol tofree aldehyde is increased. However, a phenol (including resorcinol) tofree aldehyde ratio up to 2.5 or 3.0 may be used to gain part of theadvantages if it is used soon after condensation. As the mole ratio ofresorcinol to aldehyde is decreased to less than .25 the adhesiongenerally decreases in value although such latex mixes may be verystable.

The present invention is useful in bonding natural and synthetic rubbersincluding hydrocarbon-comprising synthetic rubbers andsulfur-vulcanizable rubbers to fabrics. Examples of the rubbers soadhered are polymers of a conjugated diolefinic compound of less than 8carbon atoms including butadiene 1,3, isoprene dimethyl butadiene,cyanoprene, and chloroprene and copolymers of one or more of these witha mono-olefinic compound copolymerizable therewith including styrene,nuclearly chlorinated styrenes, 3,4, dichloralphamethylstyrene, olefinicketones including methylvinyl ketone, methylisopropenyl ketone,acrylonitrile, acrylic and methacrylic esters and the like.

In the formation of composite articles of the rubber and fabric, thevulcanizable rubber compound is cured in contact with the textile fabricwhich was first wetted with the subject adhesive dip and thereafterdried. Heat and pressure is used in forming and vulcanizing the articlesas is customary in the art. The invention is especially applicable inproducing tires, conveyor belts, and other rubber and fabric articles.

It is understood that in accordance with the provisions of the patentstatutes, variations and modifications of the invention herein describedmay be made without departing from the spirit of the invention.

Having thus described my invention what I claim is:

l. A composite article of rubber and fabric comprising textile fibershaving over surface portions thereof a mixture of (a) an unmasticatedcopolymer of 70 to 95 parts by weight of a conjugated diolefiniccompound of less than 7 aliphatic carbon atoms with 10 to 35 parts byweight of an aldehyde of the general formula where R is a bivalentaliphatic hydrocarbon radical of less than 4 carbon atoms and R' ismethyl and (b) a resinous condensation product of a phenol and analdehyde, and an in situ vulcanized rubber compound contacting thecoated surfaces of said fibers.

2. The process of adhering textile fibers to sulfur vulcanizable rubberscomprising the steps of immersing said fibers in an aqueous dispersionof (a) 70 to 95 parts by dry solids weight of a copolymer of from 65 to90 parts by weight of a conjugated diolefinic compound of less than 7aliphatic carbon atoms and from 10 to 35 parts by weight of anunsaturated aldehyde of the general formula where R is a bivalentsaturated aliphatic hydrocarbon radical of less than 4 carbon atoms andR is a member of the group consisting of hydrogen and methyl and (b) to40 parts by dry solids weight of a condensataion product of an aldehydereactive compound capable of combining with an aldehyde to form a resoletype resin, and an aldehyde, said condensation product being reacted soas to be only partially soluble in water, drying said treated, immersedfibers at 75 to 140 C. for 1 to 20 minutes, adhering the treated fibersto uncured, sulfurvulcanizable rubber, and curing said rubber in contactwith said treated fibers.

3 The process. of adhering: textile fibers to sulfur vulcanizablerubbers comprising the steps of immersing said fibers in an aqueousdispersion of (a) 70 to 95 parts by dry solidsweight of a copolymer offrom 65 to parts by weight of a conjugated diolefinic compound of lessthan 7 aliphatiecarb'onatoms and from 10" to 35 parts by weight of anunsaturated aldehyde of the general formula:

where R is a bivalent, saturated, aliphatic hydrocarbon radical of lessthan 4 carbon atoms and R is a member of the group consisting ofhydrogen and methyl and (b) 5 to 40 parts by dry solids weight of apartially water soluble resorcinol-formaldehyde condensation product,drying said treated, immersed fibers at 75 to 140 C. for 1 to 20minutes, adhering the treated fibers to uncured, sulfur-vulcanizablerubber, and curing said rubber in contact with said treated fibers.

4. A composite article of rubber and fabric comprising textile fibershaving over surface portions thereof a mixture of (a) an unmasticatedcopolymer of 70 to parts by weight of a conjugated diolefinic compoundof less than 7 aliphatic carbon atoms with 10 to 35 parts by weight ofan aldehyde of the general formula where R is a bivalent aliphatichydrocarbon radical of less than 4 carbon atoms and R is a member of thegroup consisting of hydrogen and methyl and (b) a resinous condensationproduct of a phenol and an aldehyde, said textile fibers contacting insitu a vulcanized rubber compound.

5. A composite article of rubber and fabric comprising textile fibershaving over surface portions thereof a mixture of (a) an unmasticatedcopolymer of 70 to 95 parts by weight of a conjugated diolefiniccompound of less than 7 aliphatic carbon atoms with 10 to 35 parts byweight of an aldehyde of the general formula where R is a bivalentaliphatic hydrocarbon radical of less than 4 carbon atoms and R is amember of the group consisting of hydrogen and methyl and (b) a resinouscondensation product of an aldehyde reactive compound capable ofcombining with an aldehyde to form a resoletype resin and an aldehyde.

6. A composite article of rubber and fabric comprising textile fibershaving over surface portions thereof a mixture of (a) a copolymer of 65to 90 parts by weight of butadiene and 10 to 35 parts of methacroleinand (b) 5 to 40 parts of a resorcinol-formaldehyde condensation product,said textile fibers contacting in situ a vulcanized rubber compound.

7. The process of adhering textile fibers to sulfur vulcanizable rubberscomprising the steps of immersing said fibers in an aqueous dispersionof (a) 70 to 95 parts by dry solids weight of a copolymer of 65 to 90parts of butadiene and 10 to 35 parts of methacrolein and (b) 5 to 40parts by dry solids weight of a resinous condensation product of analdehyde reactive compound capable of combining with an aldehyde to forma resole-type resin and an aldehyde, drying said treated immersed fibersat 75 to C. for l to 20 minutes, adhering the treated fibers to uncured,sulfur-vulcanizable rubber, and curing said rubber in contact with saidtreated fibers.

8. The process of adhering textile fibers to sulfur vulcanizable rubberscomprising the steps of immersing said fibers in an aqueous dispersionof (a) 70 to 95 parts by 7 M 8 dry solids weight of a copolymer of 65 to90 parts of References Cited in the file of this patent butadiene and 10t0 parts Of methacrolein and (17) UNITED STATES PATENTS 5 to parts bydry solids weight of a partially water soluble resorcinol-formaldehydecondensation product, 2499'724 Q QI 1950 drying said treated immersedfibers at to C. for 5 2561215 Mlghton July 1951 1 to 20 minutes,adhering the treated fibers to uncured, 2569'932 Izard 1951sulfur-vulcanizable rubber, and curing said rubber in con- 2615826Mallory et 1952 tact with said treated fibers.

2. THE PROCESS OF ADHERING TEXTILE FIBERS TO SULFUR VULCANIZABLE RUBBERSCOMPRISING THE STEPS OF IMMERSING SAID FIBERS IN AN AQUEOUS DISPERSIONOF (A) 70 TO 95 PARTS BY DRY SOLIDS WEIGHT OF A COPOLYMER OF FROM 65 TO90 PARTS BY WEIGHT OF A CONJUGATED DIOLEFINIC COMPOUND OF LESS THAN 7ALIPHATIC CARBON ATOMS AND FROM 10 TO 35 PARTS BY WEIGHT OF ANUNSATURATED ALDEHYDE OF THE GENERAL FORMULA
 3. THE PROCESS OF ADHERINGTEXTILE FIBERS TO SULFUR VULCANIZABLE RUBBERS COMPRISING THE STEPS OFIMMERSING SAID FIBERS IN AN AQUEOUS DISPERSION OF (A) 70 TO 95 PARTS BYDRY SOLIDS WEIGHT OF A COPOLYMER OF FROM 65 TO 90 PARTS BY WEIGHT OF ACONJUGATED DIOLEFINIC COMPOUND OF LESS THAN 7 ALIPHATIC CARBON ATOMS ANDFROM 10 TO 35 PARTS BY WEIGHT OF AN UNSATURATED ALDEHYDE OF THE GENERALFORMULA: